Four Best Practices for Precise Millimeter-Wave Measurements
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Millimeter-Wave frequency measurements require precision and care. Fortunately, the engineering challenges have become a little less daunting as more millimeter test equipment has become available. Signal analyzers have now increased direct coverage in coax to 110 GHz. This provides low noise, good accuracy, and wide bandwidth to allow engineers to focus on their designs and measurement results instead of pulling together multi-part test solutions where calibration and repeatability may be in question.
However, all this hard-won performance can be compromised if you miss even one of the fundamental practices for good measurements at these very high frequencies. The millimeter range is generally defined as 30–300 GHz, with wavelengths down to 1 mm, and these tiny wavelengths are the heart of many problems and challenges.
Connectors are a good place to start because they exemplify so many of the ways that millimeter measurements can challenge you. Figure 1 is a close-up of female and male 1 mm connectors, which are mode-free to more than 110 GHz.